CEA clearance pattern as a predictor of tumor response to neoadjuvant treatment in rectal cancer: a post-hoc analysis of FOWARC trial

Background The clinical factors that accurately predict the response to preoperative treatment in rectal cancer were yet unknown. The carcinoembryonic antigen (CEA) clearance pattern during neoadjuvant treatment has been developed and the predictive value explored in rectal cancer patients with elevated CEA levels (> 5 ng/mL). Methods The training cohort was derived from the FOWARC prospective phase III trial, and 71/483 eligible patients were included. The validation cohort consisted of 75/587 consecutive rectal cancer patients from Xiangya Hospital between 2014 and 2015. The kinetic changes in serum CEA were measured at different time points during the neoadjuvant treatment. An exponential trend line was drawn using the CEA values. The patients were categorized into two groups based on the R2 value of the trend line, which indicates the correlation coefficient between the exponential graph and measured CEA values: exponential decrease group (0.9